A manual chain block used for a load lifting operation has been conventionally known, which includes a chain block main body, an upper hook for suspending the chain block main body, a load chain looped around a load sheave of the chain block main body, a lower hook connected to a lower end of the load chain, and a hand chain looped around a hand wheel. The hand chain includes, for example, an endless chain, an endless belt or an endless rope, and has a function of transmitting operational force of an operator to the hand wheel. Similarly, the hand wheel is engaged with the endless chain, the endless belt or the endless rope to convert the operational force of the operator into rotational force.
An exemplary configuration of a manual chin block as described above is disclosed in JP 59-195193 U, for example.
As shown in FIG. 6, a manual chain block 1 has a pair of frames 2a and 2b opposed to each other with a predetermined spacing therebetween. Between these frames 2a and 2b, a base shaft 4 of a load sheave 3 is rotatably supported by bearings 4B. A drive shaft 5 is rotatably supported in a center hole 4a of the base shaft 4. A reduction gear mechanism 6 is interposed between the drive shaft 5 and the load sheave 3 such that rotational power of the drive shaft 5 is transmitted to the load sheave 3 at a decreased speed, in order to wind the load chain up and down.
The reduction gear mechanism 6 includes a pinion gear 6a provided at one end of the drive shaft 5, two first reduction gears 6b and 6b which mesh with the pinion gear 6a, second reduction gears 6d and 6d provided on gear shafts 6c and 6c of the first reduction gears 6b and 6b, and a load gear 6e which meshes with the second reduction gears 6d and 6d. In this case, in order to support the gear shafts 6c and 6c of the first reduction gears 6b and 6b, a bearing 6f is provided on the frame 2a at a position radially outside of the bearing 4B for supporting the base shaft 4 of the load sheave 3.
The drive shaft 5 has a threaded portion 7 on the other end of the drive shaft 5 opposite to the pinion gear 6a. A mechanical brake 9 with a hand wheel 8 is screwed onto the threaded portion 7.